Just got a new compressor and I wondering if I should be releasing all of the pressure out of the unit when it is not in use? Or is it better to leave the pressure in so that the unit does not have to work as hard to build up the pressure next time?

I am not planning on using the unit daily. Mostly for weekend projects and regular maintenance (airing up car tires... etc).

SCUBA tanks are stored at between 25 and 300 psi (consider they normally hold 3000 psi), specifically to prevent moisture from entering the tank. Does the same theory not hold true for these tanks as well? There is a major difference in the air though: that air that goes into SCUBA tanks goes through a moisture separator and filters to make it moisture- (and oil-) free.
– gregmacJan 27 '12 at 16:29

It may depend on the tank size. I've got a 1 gallon DeWalt, and it says the same thing. What about something like a 60 gallon compressor though? That's going to take a lot more work to re-pressurize than a few gallon compressor.
– DoresoomDec 2 '10 at 17:34

8

Larger compressors (and even many smaller ones) will have a water drain at the bottom of the tank that can be used to get the water out. Open it until air comes out instead of water, and you can then close it leaving most of the pressure still in the tank.
– Mike PowellDec 2 '10 at 17:53

@Mike: That makes sense. I was thinking small picture - if I open the valve on my one gallon tank, it's empty in a few seconds.
– DoresoomDec 2 '10 at 21:34

Yes, definitely drain it after each use. Need to avoid letting water pool in the tank, possibly corroding and weakening it. Release the air and open the drain valve for a while to let out any condensation.

I always drain my compressor when finished, mainly to blow out any moisture that could have built up inside. You should vent the air through the valve on the tank itself (facing towards the ground) for at least the last 40-60 lbs of air to help blast out and remaining moisture. I also always leave the tank valve open and facing down to help keep it dry inside.

Vent it with the valve facing towards the ground. On the compressor I've used before, the vent was up the side a little bit. If you just opened the valve, there would still be a pool of water in the bottom.
– tehDorfJun 19 '15 at 21:48

If you open drain valves too quickly moisture that settles to the bottom of the tank gets dispersed. Crack valves SLOWLY till water starts to drip to allow water accumulated at the bottom of the tank to drip out. That is all you need to do on a daily basis. If it makes you feel better you can drain tanks completely every couple of weeks. The only reason I can see to relieve all pressure is to relieve high pressure from the regulator in order to protect seals. I make a habit of draining pressure down to 50 lbs daily for this purpose.

Release the pressure. If you are carrying a pressurized canister and you, say, drop it on a concrete floor, it could fracture, sending shrapnel everywhere. In other words, a pressurized canister is a bit like a small bomb.